package me.ezitku.base.PrefHelper;

/**
 * Created by yurqi on 11/24/2016.
 */

import android.os.Build;

import java.nio.charset.StandardCharsets;
import java.security.CryptoPrimitive;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class AES {
    public static String encrypt(String key, String data)
            throws Exception {
        byte[] rawKey = getRawKey(key.getBytes());
        byte[] result = encrypt(rawKey, data.getBytes());
        return toHex(result);
    }

    public static String decrypt(String key, String data)
            throws Exception {
        byte[] rawKey = getRawKey(key.getBytes());
        byte[] enc = toByte(data);
        byte[] result = decrypt(rawKey, enc);
        return new String(result);
    }

    private static byte[] getRawKey(byte[] seed) throws Exception {
        //9.0兼容发
        byte[] raw = InsecureSHA1PRNGKeyDerivator.deriveInsecureKey(seed, 16);

//        KeyGenerator kgen = KeyGenerator.getInstance("AES");
        //7.0 后不兼容
//        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG", "Crypto");
        //7.0 后兼容
        //可是 9.0不兼容
//        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG", new CryptoProvider());
//        sr.setSeed(seed);
//        kgen.init(128, sr);
//        SecretKey skey = kgen.generateKey();
//        byte[] raw = skey.getEncoded();
        return raw;
    }

    private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec, new IvParameterSpec(
                new byte[cipher.getBlockSize()]));
        byte[] encrypted = cipher.doFinal(clear);
        return encrypted;
    }

    private static byte[] decrypt(byte[] raw, byte[] encrypted)
            throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(
                new byte[cipher.getBlockSize()]));
        byte[] decrypted = cipher.doFinal(encrypted);
        return decrypted;
    }

    private static String toHex(String txt) {
        return toHex(txt.getBytes());
    }

    private static String fromHex(String hex) {
        return new String(toByte(hex));
    }

    private static byte[] toByte(String hexString) {
        int len = hexString.length() / 2;
        byte[] result = new byte[len];
        for (int i = 0; i < len; i++)
            result[i] = Integer.valueOf(hexString.substring(2 * i, 2 * i + 2),
                    16).byteValue();
        return result;
    }

    private static String toHex(byte[] buf) {
        if (buf == null)
            return "";
        StringBuffer result = new StringBuffer(2 * buf.length);
        for (int i = 0; i < buf.length; i++) {
            appendHex(result, buf[i]);
        }
        return result.toString();
    }

    private final static String HEX = "0123456789ABCDEF";

    private static void appendHex(StringBuffer sb, byte b) {
        sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
    }



}
